A recessive genetic condition occurs when both copies of a particular gene have pathogenic variants. If you have one copy of a gene with a variant and one normal copy of that same gene, you are considered a "carrier" for that recessive genetic condition even though you are not affected by it.

In order for carriers to have a child affected by a recessive genetic condition, both partners would have to be carriers of the same condition.

A dominant genetic condition occurs when one of the two copies of a particular gene has a pathogenic variant. Only one of the copies of the gene needs to have a pathogenic variant in order for an individual to be affected by a dominant genetic condition (recessive conditions require both copies to have variants). If either you or your partner have a dominant genetic condition, you have a 50% risk of having a child affected by that condition.

The X and Y chromosomes (often called the sex chromosomes) determine whether a baby is male or female. Males have one X and one Y chromosome, while females have two X chromosomes. Some disorders are caused by pathogenic variants of the X chromosome. Generally, if a woman has a pathogenic variant in a gene located on an X chromosome, she is considered a carrier — and has a 50% chance of passing that variant onto her children. If she passes on the variant on to a male child, that child can be affected with the condition. Affected males will not pass the variant onto their sons, but daughters of affected males will be carriers of the variant. Female carriers rarely develop symptoms of the condition but their daughters have a 50% chance of being carriers.